/*
 * Copyright 2007 ZXing authors
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.jwetherell.quick_response_code.qrcode.decoder;

import com.google.zxing.common.BitMatrix;

/**
 * <p>
 * Encapsulates data masks for the data bits in a QR code, per ISO 18004:2006
 * 6.8. Implementations of this class can un-mask a raw BitMatrix. For
 * simplicity, they will unmask the entire BitMatrix, including areas used for
 * finder patterns, timing patterns, etc. These areas should be unused after the
 * point they are unmasked anyway.
 * </p>
 * 
 * <p>
 * Note that the diagram in section 6.8.1 is misleading since it indicates that
 * i is column position and j is row position. In fact, as the text says, i is
 * row position and j is column position.
 * </p>
 * 
 * @author Sean Owen
 */
abstract class DataMask {

    /**
     * See ISO 18004:2006 6.8.1
     */
    private static final DataMask[] DATA_MASKS = { new DataMask000(), new DataMask001(), new DataMask010(), new DataMask011(), new DataMask100(),
            new DataMask101(), new DataMask110(), new DataMask111(), };

    private DataMask() {
    }

    /**
     * <p>
     * Implementations of this method reverse the data masking process applied
     * to a QR Code and make its bits ready to read.
     * </p>
     * 
     * @param bits
     *            representation of QR Code bits
     * @param dimension
     *            dimension of QR Code, represented by bits, being unmasked
     */
    final void unmaskBitMatrix(BitMatrix bits, int dimension) {
        for (int i = 0; i < dimension; i++) {
            for (int j = 0; j < dimension; j++) {
                if (isMasked(i, j)) {
                    bits.flip(j, i);
                }
            }
        }
    }

    abstract boolean isMasked(int i, int j);

    /**
     * @param reference
     *            a value between 0 and 7 indicating one of the eight possible
     *            data mask patterns a QR Code may use
     * @return DataMask encapsulating the data mask pattern
     */
    static DataMask forReference(int reference) {
        if (reference < 0 || reference > 7) {
            throw new IllegalArgumentException();
        }
        return DATA_MASKS[reference];
    }

    /**
     * 000: mask bits for which (x + y) mod 2 == 0
     */
    private static class DataMask000 extends DataMask {

        @Override
        boolean isMasked(int i, int j) {
            return ((i + j) & 0x01) == 0;
        }
    }

    /**
     * 001: mask bits for which x mod 2 == 0
     */
    private static class DataMask001 extends DataMask {

        @Override
        boolean isMasked(int i, int j) {
            return (i & 0x01) == 0;
        }
    }

    /**
     * 010: mask bits for which y mod 3 == 0
     */
    private static class DataMask010 extends DataMask {

        @Override
        boolean isMasked(int i, int j) {
            return j % 3 == 0;
        }
    }

    /**
     * 011: mask bits for which (x + y) mod 3 == 0
     */
    private static class DataMask011 extends DataMask {

        @Override
        boolean isMasked(int i, int j) {
            return (i + j) % 3 == 0;
        }
    }

    /**
     * 100: mask bits for which (x/2 + y/3) mod 2 == 0
     */
    private static class DataMask100 extends DataMask {

        @Override
        boolean isMasked(int i, int j) {
            return (((i >>> 1) + (j / 3)) & 0x01) == 0;
        }
    }

    /**
     * 101: mask bits for which xy mod 2 + xy mod 3 == 0
     */
    private static class DataMask101 extends DataMask {

        @Override
        boolean isMasked(int i, int j) {
            int temp = i * j;
            return (temp & 0x01) + (temp % 3) == 0;
        }
    }

    /**
     * 110: mask bits for which (xy mod 2 + xy mod 3) mod 2 == 0
     */
    private static class DataMask110 extends DataMask {

        @Override
        boolean isMasked(int i, int j) {
            int temp = i * j;
            return (((temp & 0x01) + (temp % 3)) & 0x01) == 0;
        }
    }

    /**
     * 111: mask bits for which ((x+y)mod 2 + xy mod 3) mod 2 == 0
     */
    private static class DataMask111 extends DataMask {

        @Override
        boolean isMasked(int i, int j) {
            return ((((i + j) & 0x01) + ((i * j) % 3)) & 0x01) == 0;
        }
    }
}
